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tubes, and the two fused tubes will give rise to a third common conidium-bearing tube. Sometimes this tube is extremely long and fine, and furnished with numerous joints throughout its entire length. The conidia, as produced by the germ-tubes, are capable of producing other conidia by budding, till at last large colonies of conidia are produced in a yeast-like condition, free from the original Ustilago spore and its septate germ tube. The conidia, which are very unequal in size, germinate as at 7 and 8. Germination may take place at one or both ends or one or both sides, and the germ-tubes may fuse with each other at any point of contact. Sometimes the germtubes produced by the conidia are of almost inconceivable fineness and attenuation, but always more or less jointed throughout their entire length; the contained vital material is generally most abundant at the growing end. Sometimes, when growth has quite ceased, owing to unfavourable conditions, it is renewed with vigour under changed conditions, and new colonies of yeast-like conidia are formed, either from old threads or old conidia.

In the allied fungus named Ustilago antherarum, Fr., the conjugation of cells is very clearly seen, and lateral conidia are produced, as in Tilletia, Fig. 116, D, G. This parasite is common on the flowers of Silene, Lychnis, etc., in fields and hedge sides, reducing the anthers with their pollen to black dust. The conjugation is also very distinct in the spores of Ustilago longissima, Tul.; common on Poa aquatica, L., and P. fluitans, Scop. No doubt the so-called conjugation of cells is potential in all species of Ustilago and its allied genera.

We recently observed the germination of the spores of Ustilago carbo, Tul., under curious and natural conditions. We placed a large number of spores on the top of a flower-pot filled with moist white sand to note whether the spores would be readily filtered through the mass by rain. They did so filter in large numbers; but many of the spores germinated on the top stratum of sand, and

vast quantities of the transparent conidia were filtered through the sand on to the plate below; and in this posi tion, beneath the bottom of the flower-pot and in the plate, they formed colonies of yeast-like conidia, and these conidia germinated by producing threads, as we have illustrated them in Fig. 121, 7 and 8. The spores germinate very readily and produce yeast colonies in diluted beer and diluted expressed juice of horse-dung.

The disease is doubtlessly propagated by the spores of the fungus being blown over the fields and absorbed by the earth, and by the fungus spores which adhere to the seed at the time of sowing. The black spores germinate in the ground, and there produce the secondary and tertiary series of transparent spores illustrated in Fig. 121. These spores or conidia of the second and third order at length protrude extremely fine germinal threads, and these threads find their way into the earliest produced stomata of the infant plant. The spawn or mycelium then travels up the stem towards the panicle and attacks the lowermost spikelets first. We have never noticed the upper part of a panicle diseased whilst the lower part has been sound. It may be commonly noticed that every stem, from two to eight or more, on an invaded plant, will show the disease, whilst adjoining plants remain free. The evidence therefore seems complete that the infection comes from the ground and travels upwards. It is obvious, therefore, that smut can only be prevented by dressing the seed, as in the case of bunt, and the directions for one apply to the other. remedy against smut, much in favour in the north of England, and one which is said to never fail, is the preparation of the seed, immediately before sowing, with a sprinkling of stale urine, the seeds being afterwards raked in powdered quicklime till the seed is white. Sometimes the seed is prepared with vitriol or sulphate of copper solution, or bluestone" dissolved in boiling water. One pound of "bluestone" dissolved in five quarts of water

66

A

The

is sufficient for a sack of four imperial bushels. wheat is soaked for ten minutes, or the ten pints of solution may be poured over till all is absorbed.

Bunt, Tilletia Caries, Tul., is almost confined to two species of Triticum; but as smut invades many grasses found in pastures and waysides, the disease is clearly often nursed by the weeds. This fact points to the necessity All smutted grasses, as

for clean and careful farming.

well as the smutted panicles of oats, wheat, and barley, should be gathered in their earliest recognisable stages and burnt. A few common-sense hints given to the labouring men and boys would often save the employer from great losses.

The smut fungus Ustilago carbo, Tul., has been met with on the following grasses :-—Andropogon hirtus, L.; Cynodon Dactylon, L.; hair grass, Aira cœspitosa, L.; oats, Avena sativa, L.; yellow oat grass, A. flavescens, L.; downy oat grass, A. pubescens, L.; Arrhenatherum avenaceum, Beauv.; species of Melica; fescue grass, Festuca pratensis, Huds.; Brachypodium ciliatum, P.B.; wheat, Triticum vulgare, Vill.; T. turgidum, L.; barley and barley grasses, Hordeum distichum, L.; H. murinum, L.; H. vulgare, L.; rye, Secale cereale, L.; rye grass, Lolium perenne, L.; darnel grass, L. temulentum, L.; rice, Oryza sativa, L.; and no doubt other plants. The different species of millet or sorghum, which in the south of Europe and some parts of Asia are grown for bread in the place of the oats and barley of northern Europe, are sometimes badly smutted. Sorghum vulgare, P., and Setaria italica, Beauv., are the chief food plants affected in India, Arabia, Asia Minor, Spain, and Italy.

Dr. Maxwell T. Masters, F.R.S., has recently detected a new British smut fungus, Ustilago Kuhniana, Wolff, on Rumex Acetosa, L.; and a second new species, U. Candollei, Tul., has been found on Polygonum.

CHAPTER XXXII.

TARE OR VETCH, AND PEA MOULD.

Peronospora viciæ, Berk.

LIKE several other species of Peronospora described in this work, P. vicia was first detected by the Rev. M. J. Berkeley, and described and illustrated by him in vol. i. of the Journal of the Royal Horticultural Society in 1846.

This parasite is frequent on the under surface of the leaves of tares or vetches and field and garden peas. Although allied to Peronospora trifoliorum, D.By., as illustrated at Fig. 1, and P. exigua, W.Sm., Fig. 2, it is clearly distinct from both. Like the two plants just described, it grows within the foliage and causes brownish downy patches on the leaves and putrescence of the tissues. The conidiophores of the fungus grow in clusters, the spores are supported on long extremely slender spicules, and are tinted with a dull gray colour. Peronospora viciæ, Berk., is illustrated, enlarged 400 diameters, at Fig. 122; a single spore or conidium is farther enlarged to 1000 diameters at A. The spores on germination do not burst at the apex, but the germtube is generally protruded from the side. Damp close weather greatly favours the extension of this fungus, and dry weather retards its growth. It unfortunately happens that late peas are sometimes quite destroyed by another fungus named Erysiphe Martii, Lk., whose growth is favoured by dry weather and retarded by wet. When both fungi are present on one crop the destruction of peas is complete.

The resting-spores are brown, and at length reticulated

•X.400

B

X-400

X-1000

FIG. 122.-TARE OR VETCH, AND PEA MOULD.
Peronospora viciæ, Berk. Enlarged 400 diameters.

Conidium, A, 1000 diameters; Oospore, B, 400 diameters.

by the shrinking of the outer coat as illustrated, enlarged 400 diameters, at B. All diseased and decaying tare and

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